Percussive tool



Oct. 1, 1946. A. R. scHwARzKoPF PERCUS S IVE TOOL Filed Nov. 6, 1943 Patented Oct. 1, 1946 UNITED STATES PATENT OFFICE PERCUSSIVE TOOL y Arthur R. Schwarzkopf, Chicago, Ill., assigner to Wodack Electric Tool Corporation, Chicago, Ill., a corporation of Illinois Application November 6, 1943, Serial No. 509,311

8 Claims. (Cl. Z55-42) The invention relates to power operated hammers or percussive tools and more particularly to portable tools in which the power is supplied by a rotary motor.

In tools of the above general character' a heavy power spring is utilized to drive the reciprocatory impact member against a tool bit such as a star drill which is loosely held in a socket provided for that purpose. Retraction of the impact member to condition the spring for action is effected by the motor through the medium of an actuating mechanism usually in the form of a cam. In normal operation when the tool bit is held firmly against a workpiece, substantially the entire force imparted to the impact member by the power spring is absorbed by the tool bit. When the motor is run idly, that is, Without a tool bit in the socket or when the pressure on the bit is relieved, the shock of stopping the impact member must be absorbed within the tool itself. In percussive tools as constructed heretofore, the shock is ordinarily taken by the actuating mechanism or cam resulting in excessive wear or damage to the same.

One object of the invention is to provide novel means for effectually absorbing the shock of theimpact member without subjecting the actuating mechanism to excessive wear or strain when the motor is run idly.

Another object is to provide novel means for absorbing the shock of the impact member which permits the full driving power of the power spring to be utilized in the normal operation of the tool.

Still another object is to provide a percussive tool of novel and advantageous construction in which the power spring is enabled to effectually absorb the shock of the impact member when the tool is run idly.

It is also an4 object of the invention to provide a percussive tool in the nature of an attachment suitable for use with an ordinary portable electric drill or the like which is simple and relatively inexpensive to manufacture, which is rugged and durable in construction and Which is enicient in operation.

Other objects and advantages of the invention will become apparent from the detailed description of the preferred embodiment illustrated in the accompanying drawing in which:

Figure 1 is a longitudinal sectional view of a percussive tool embodying the features of the invention.

Fig. 2 is a sectional View similar to Fig. 1 showing the impact member in retracted position.

Fig. 3 is a fragmentary sectional view similar 2 to Figs. 1 and 2 but showing the impact member in its extreme advanced position.

Fig. 4 is a fragmentary sectional view of a modied form of the tool.

Fig. 5 is a perspective view of the actuating cam.

Fig. 6 is a perspective view of the cam follower which is adapted to cooperate with the cam shown in Fig. 5.

While the invention is susceptible of various modifications and alternative constructions, I have shown in the drawing and will herein describe in detail the preferred embodiment, but it is to be understood that I do not thereby intend to limit the invention to the specific form disclosed, but intend to cover all modifications and alternative constructions falling within the spirit and scope of the invention as expressed in the appended claims.

The improved percussive tool, in the form selected for illustration, comprises generally an elongated cylindrical casing or barrel Ill preferably in the form of a hollow casting. At one end, the barrel is provided with a socket II for receiving the shank of a tool bit While the other end is suitably shaped so that it may be frictionally clamped to the spindle hub of an electric drill I2 or similar power driven tool. Supported within the barrel coaxial with the socket II is a reciprocable impact member or plunger I3. As herein shown the socket II is formed in a plug I4 threaded into the barrel and its inner end is splined for coaction with corresponding splines I5 on the impact member thus providing a sliding bearing for the member while effectually holding it, against rotation.

The impact member I3 is yieldably held in a centered position in the housing by means of an extensible power spring I6. As herein shown, the spring I6 is arranged to act between the impact member and a `pair of spaced abutments I1 and I8 rigid with the barrel Ill. In the exemplary tool, the abutment I'l is formed integrally with the barrel I0 While the abutment I8 is formed by the inner end of the plug I4. The force of the spring is exerted on the impact member through the medium of a collar I9 interposed between the end of the spring and an upwardly facing shoulder 2D formed on the member adjacent the splined end. Movement of the impact member toward the socket under the action of the spring I6 isk thus limited by engagement of the collar I9 with the fixed abutment I8, the shoulder and abutment being located so that the end of the plunger projects into the socket II a sufficient distance to engage the shank ofthe tool bit held therein.

Suitable actuating means is provided for periodically retracting the plunger i3 from the socket II against the forceV exerted by the spring I'o and for releasing the member for impact with the tool bit. The actuating means is arranged to be driven by the motor of the drill I2 to which the tool is attached and, as herein shown, comprises a rotary cam member 2l, preferably of cylindrical form. The cam member is formed with an end wall 22 adapted to rest on an anti-` friction thrust bearing 23 seated in a counter.- :bore in the barrel l immediately above abutment Il.

approximately 180 and terminating in abrupt .faces 2.5.

For coaction with the cam member, a cam follower 25 is threaded on the upper end of the impact member i3; The cam follower, as shown in Fig. 6, comprises a collar having arms 2ll pro# jecting radially from opposite vsides for engagement with the cam surfaces 2li. Since the plunger I3 is held against rotation by its splined connection with the plug i4, rotation of the cam member ZI is thus effective to retract the follower 25 and impact member I3 against the force of the power spring IE. When the cam surfaces 24 ride out from under the follower arms, the abrupt faces 25 of the cam member permit the plunger to advance rapidly under the actio-vi of the spring i6 and thus deliver a powerful im# pact to the tool bit. Y

Rotation of the cam mem-ber 2l is eieced through the medium of a power transmitting c' 'nnection with the driven spindle of the drill I2. rhis connection, as herein shown, comprises a cup-shaped head 3i! enclosing the cam member and threaded thereto as shown in Figs. 1 4. At its upper end, the head 3E is provided with an axially projecting shank 3i adapted .to be. se` cured in a colletchuck 32 or the like fast on the end of the drill spindle. The sides of the barrel ISB are preferablycut away adjacent the head 353 and chuck 32 to provide kconvenient ac cess to these parts V`for connecting and discon necting the tool and drill. Y

In the normal operation of the tool, that is, when the tool bit is held against the work with a substantial amount of pressure, the impact of the member I3` is absorbed by the tool bit. However, when the tool is runidly either without a tool bit in the socket or when the bit is not held rmly against the work, allora part of the impact of the member I3 must be absorbed within the tool itself. ln accordance with the'present invention, advantage is taken of the fact that the driving action of thepower spring is ter- Aminated at a definite point in the advance o the impact member to utilize the power Spring itself to absorb the impact of the member after the driving force of the spring has been expended.

To enable the spring I6 to perform its shock absorbing function, the impact member I3 is fit1 ted with a sleeve 35;, which may also be referred to as a motionor force-transmitting member, having at one end a peripheral ilense inter-l posed between the abutment Il and theupper end of the power Spring l5, The sleeve is Supl@ ported and guided for axial sliding movement in a central bore in the'abutment Il and it extends through the bearing 23 and end wall 22 of the As will be seen by reference to.` Fig. 5, the open end of the cylindrical wall of the cam member 2l is shaped to provide two inf clined cam surfaces Ztl each extending throughl normal rest position as shown in Fig. 1.A

vpower spring I6.

cam member to bear against a collar 2l loosely mounted on the plunger below the cam follower 26, A groove B in the face of the collar prevents binding of the same `on the impact member in theY event that the collar is deformed by theV pounding of the cam follower thereon.

The sleeve .35 and collar 3l" are dimensioned and arranged so that the follower 25 rests on the upper surface of the collar and the follower varms Zl are held out of engagement with the cam surfaces Zfi when the impact member I3 is in its v As the cam is rotated, the cam surfaces 2li engage the El thus retracting the impact member from the Ysocket and compressingrthe spring it between the collar It and Vflange 36 ofY the sleeve 35. When the cam surfaces lride out from under the follower arms, the spring I5 advances the impact member rapidly toward the socket. n the event that rno resistance is presentediosuoh movement, as byY a tool bit, the inertia `of the impactmemgbe'rrcarries it beyond the` normal restposition and the impact' ofthe member IS falls lliBOn the collar 31 instead of on tbe oem and follower'` arms 2l.. Tbe'foree'of the impact is transferred from the Collar through the sleeve 35 and fiange 36 to the upper' end 'of the The action above described takes place only after the power `spring `has expended its power to advance the impact member as determined by the engagement of the collar i9 with' the nxed abutment i8. The power spring thus brings .the impact member to a cushioned stop .and absorbs the shock incident thereto without sacriceo'f normal operating efficiency. In this way a single spring is enabled to 'function both as 'the Vdriver for the 'impact member in the normal operation of the tool and as a buffer or shock absorber when the tool .is run idly. The use of a single spring for this purpose materially Simp-lines the construction of the tool and correspondingly reduces its cost, Moreover, the operating efficiency. of the powerspring is not impaired since the shock ab-A sorbing. action takes place only after the spring has advanced the'impactr member to the full extent permitted in normal operation.

' The modified construction shown in Fig. 4 is similar in general to that above described except that a sleevev lil which corresponds in function to the sleeve 35 is formed with an integral ange or coilar 4I at its upper end for engagement ,with the lower face of Ythe, camrffollowerl.' YThis ange is recessed as' at 42 to prevent bindingon the plunger inthe eventI thatfthe flargeisfde-j formed by the pounding of the fo1lower.` lit .lits lower end, the sleeve 40 abuts `against a washer 43 looselymounted on the impact member I3' and interposed between the abutment ll and the upper end of the power spring 16. In this in-Y stance, the impactofthe memberlt is taken by the ange 4| and transferred through the sleeve 4t and washerfii to the power spring which'thus brings the plunger to a cushioned stop without imposing unnecessary strains on the cam or lon the parte of the follower coacting therewith.

. It will be apparent V from theforegoing that the invention provides a percussive tool of novel and advantageous construction embodying improved means for absorbing vthe vimpact of the impact member when thetool is run id1y By reason of the improved construction, the'power' spring itself is enabled to function as va buffer or shock absorbing means without in the least impairing its normal operating efficiency.' The improved tool is simple and relatively inexpensive to manufacture, very rugged and durable in construction and eicient in operation,

claim as my invention:

l. A hammer attachment for rotary drills comprising, in combination, an elongated barrel adapted to be mounted on the drill and having a tool socket, an impact member reciprocable axially in the barrel in operative relation to the socket, means forming shoulders adjacent opposite ends of said member, a pair of spaced abut- 'mentsv in said barrel, a collar loosely mounted on said--member and abutting against the shoulder adjacent one end of the member, a flanged sleeve slidably mounted on the member and abutting against the shoulder adjacent the other end of the member, a spring interposed between said collar and said sleeve operative to yieldably urge the collar and the flange of the sleeve against said abutments whereby to hold the member in a central position in the barrel, power driven means acting on said member to retract the same from the socket, the shoulder at said one end of said member engaging said collar in the retraction of the member to compress said spring bey tween said collar and said sleeve, said spring acting through said collar and said shoulder upon the release of the member to advance it rapidly toward the socket, said sleeve being engaged by the shoulder adjacent the other end of said meinber for movement therewith at a predetermined point in its advance and said spring acting to resist such movement of the sleeve and therebl7 bring the member to a cushioned stop.

2. A hammer attachment for rotary drills comprising, in combination, a barrel adapted to be mounted on the drill and having a tool socket, an impact member reciprocable axially in the barrel in operative relation to the socket, a pair of members slidably mounted on said impact member, means limiting the movement of the sliding members toward the respective ends of the impact member, a spring interposed between said sliding members yieldably urging them toward their limit positions, abutment means in said barrel engageable by the sliding members at their limit positions, power actuated means operable to intermittently retract the impact member from the socket and to release the same, one of said sliding members moving with the impact member in its retraction through the action of said limiting means to compress said spring against the other sliding member held against movement by its associated abutment, said spring acting through said one sliding member and its associated limiting means when the impact member is released to advance the impact member rapidly toward the socket, said other sliding member being carried along by the impact member after a predetermined advance through the action of its associated limiting means and acting to compress said spring against said one sliding member held stationary by its associated abutment whereby the impact member is brought to a cushioned stop.

3. A percussive tool comprising, in combination, a casing, an impact member supported for reciprocation in said casing, a flanged sleeve mounted on said member and seated on said casing, spring means interposed between said member and the anged end oi said sleeve operative to urge the member outwardly of the casing, rotatably driven cam means operative to intermittently retract the member against the pressure of said spring means and to suddenly release 6 the member to `the action of the spring, and means reciprocable with said member engageable with the other end of the sleeve to interrupt the outward movementv of the member by said spring means. l

fl. Apercussive tool comprising, in combination, a casing having 'a tool socket at one end, an elongated impact member supported in said casing for reciprocation axially toward and from the socket, a flanged sleeve slidably mounted on said member, a cam follower at one end oi the member engageable with one end of the sleeves a fixed abutment in said casing, spring means yieldably urging the flange oi said sleeve against said abutment, power actuated cam means operative to retract the impact member against the force of said spring and to release the member for movement toward the socket under the action of said spring, said follower engaging said sleeve to transfer the impact oi the member to said sleeve after a predetermined advance of the member.

5. A hammer attachment for rotary drills and the like comprising, in combination, an elongated barrel having a tool socket at one end, means at the other end of the barrel for mounting it on the drill, an impact member reciprocable axially in said barrel in operative relation to said socket, a driving spring interposed between said barrel and said member operative to yieldably urge the member toward said socket, a cam follower rigid with said impact member, a cam arranged to be driven by the drill and operative in coaction with said follower to periodically retract the impact member from said socket and then release the member, said spring storing up energy incident to suoli retraction for advancing the member rapidly toward said socket upon its release, stop means including a sleeve element slidable relative to said impact member and yieldably urged away from said socket by said spring, a collar interposed between said sleeve element and said follower, said collar being positioned for engagement by said follower before the follower engages said cam in the advance of said impact member whereby the energy of said impact member is transferred to said spring to cushion the impact of the member.

6. In a percussive tool, in combination, a casing having a tool socket at one end, an elongated impact member supported in said casing for reciprocation axially thereof toward and from said socket, a flanged sleeve slidably mounted on said member, a rigid element adjacent one end of said impact member positioned for coaction with one end of said sleeve, a xed abutment in said casing, spring means interposed between said sleeve and said impact member yieldably urging the flange of said sleeve against said fixed abutment and said impact member toward said socket, power actuated means operative to retract the impact member against the force of said spring and to release the member for movement toward the socket under the action of said spring, said rigid element acting through said sleeve to transfer the impact of the member through said sleeve to said spring upon a predetermined advance of the member whereby to bring the member to a Cushioned stop.

7. A percussive, tool comprising, in combination, an elongated barrel having a tool socket at one end, an impact member supported in said barrel for reciprocation relative to said socket, power actuated means for retracting said member from said socket and for releasing it, a power spring adapted to be stressed in response to the 7 retraction of said impact member and operative upon release of the member to advance lit t0 engage a tool bit in said socket, and a force transmitting member movable with said impact member during the latter portion of the travel thereof forvengaging said spring and thereby for rendering said spring operative to absorb the impact and bring said member to a cushioned stop when the resistance offered by the tool bit to such advance is insuicient to absorb the impact.

8. A percussive tool comprising, in combination, a casing having a tool socket at one end, an impact member reciprocable axially in the casing in operative relation to said socket, a member mounted for limited axial movement relative to said impact member and for limited axial movement relative to said casing; a power Spring interposed between said members yieldably urging the movable member` against the casingand the impact member toward the socket, power actuated means loperative to intermittently retract the impact member from the socket and thereby com,- press said .Spring against said movable member and to release the impact member to theV action of the compressed spring, and means associated with said iinpact member engageable with said movable ,member at'a'predetermined point in the advance Q f the impact member to compressthe Spring-against the impact member and thereby bringfthe latter to a cushioned stop.

ARfrHUR R. .SCHWARZKOPR 

